1. Field of the Invention
The present invention relates to an improvement in a magnetic disk apparatus for reading and writing information to a magnetic disk, used as a storage apparatus for a computer apparatus.
2. Description of the Related Art
FIGS. 10A and 10B are drawings showing a magnetic disk apparatus; a cross sectional view (FIG. 10A) and a view from above (FIG. 10B) are shown. Also, FIG. 11 is a view from above of the magnetic disk apparatus with the cover 8 in FIGS. 10A and 10b removed. In FIG. 10A, a DC motor 2 is mounted on the base 1. At least one magnetic disk 3 is mounted on the DC motor 2 so as to be capable of rotating about the center of the DC motor 2. In FIG. 10A, five magnetic disks 3, for example, with spacers 4 fitted between them, are pressed together by a screw fastening using a disk clamp 5, and are mounted on the DC motor 2. Also, as shown in FIG. 11, an actuator arm 6 is disposed with a head 7 for reading from and writing to the magnetic disk 3, the aforementioned head being mounted on the end of the aforementioned arm.
The cover 8 shown in FIG. 10A and 10B encloses the abovementioned constituent elements. The cover 8 comprises a recessed portion; a damping plate 9 is attached to the outer surface thereof using an element made of a viscoelastic material. In this way, noise generated by the magnetic disk apparatus can be suppressed to a certain extent.
The performance of such magnetic disk apparatuses has improved markedly in recent years, but further noise reductions are required.
Also, higher density storage capacities and increased access speeds for the magnetic disk apparatuses are required. One method of increasing the density of storage capacity may be to reduce the track pitch on the magnetic disk, for example. One method of increasing access speed may be to raise the speed of rotation of the magnetic disk.
However, simply narrowing the track pitch on the magnetic disk, or simply raising the speed of rotation of the magnetic disk, results in decreases in the signal to noise (S/N) ratio of the positioning error signal, which indicates the displacement of the head in relation to the track. One cause of this is known to be the disk resonance due to disk rotation. The position detection precision of the heads drops due to the decrease in the S/N ratio of the positioning error signal so that the probability of operating errors such as reading errors becomes high. Consequently, means for suppressing magnetic disk resonance are being sought.
Furthermore, a magnetic disk in a magnetic disk apparatus is attached with a disk clamp as discussed above. However, there is a risk that the position of the magnetic disk will be displaced within the magnetic disk apparatus by a shock or the like (the displacement is in units of microns). Major problems such as errors in accessing the magnetic disk occur as a result of the displacement of the position of the magnetic disk. Improvement to the shock-resistance performance is also required for this reason.